Who Killed the College Dean?
A Logical Murder Mystery
Christopher La Barbera, Ph.D.
Department of Humanities, Colby-Sawyer College
Subject Areas: Logic, Philosophy
Course level: 100
Quantitative concepts/skills: Deductive reasoning from premises to
conclusion (logical necessity and inference), logical argumentation with
statement-based logic, formal argument patterns (statement and predicate
based), symbolic logic.
Overview: This assignment is used in my class as an application of formal
argument patterns to a “real world” mystery. Students are asked to infer the
location, weapon and suspect in a murder from a variety of statements about
the crime scene.
Background: Students in PHI 110 (Introduction to Logic) are taught a
general competency in formal logic, including statement-based and
predicate-based patterns. This activity tests their comprehension of some
common argument patterns, including modus ponens, modus tollens,
disjunctive arguments, hypothetical arguments, predicate instantiation and
universal syllogisms. While the students in the course are familiar with the
formal versions of these argument patterns, general “informal” logical
deductions may also be used to solve the activity.
Outcomes or learning goals: The goal of this activity is for students to
apply logical deductive principles to solve a murder mystery with various
pieces of evidence. In the process, the students use the evidence by choosing
the relevant statements, in order to show which conclusions are logically
necessary. The students must also eliminate and not be confused by
statements that are not relevant to the deductions necessary to solve the
murder. The students apply deductive reasoning skills to infer which of the
locations, weapons and suspects is logically necessitated by the evidence.
Attached materials: Main activity, solution.